Deltoid bursitis and other shoulder conditions that may develop after vaccination injections into the deltoid muscle are painful, but they’re also rare and preventable, according to a new study.
Doctors and patients have long been familiar with shoulder problems after intramuscular vaccination into the deltoid, but epidemiologic studies that shed light on the problem have been limited, the authors write in Annals of Internal Medicine.
“This large population-based study found a small risk for shoulder conditions after intramuscular vaccination,” lead study author Chengyi Zheng, PhD, a principal research informatics specialist in the Department of Research & Evaluation of Kaiser Permanente in Pasadena, California, told Medscape Medical News.
“We found increased incidence of shoulder conditions after vaccination based on age and female sex, as well as [after multiple] simultaneous vaccinations among elderly persons, who generally have lower muscle mass and may be more prone to needle overpenetration,” he added.
Dr Chengyi Zheng
To estimate the risk for shoulder conditions after vaccination and assess possible risk factors, Zheng and colleagues conducted a retrospective cohort study within the large integrated healthcare system Kaiser Permanente Southern California. They analyzed data from system members aged 3 years and older who received any intramuscular vaccination to the deltoid over a 21-month pre-COVID period beginning in April 2016.
The researchers used a natural language processing (NLP) algorithm that recognized shoulder disorder diagnosis codes to identify all potential shoulder conditions and confirmed each identified case with the patient’s chart. They then compared the characteristics of vaccinated patients with and without shoulder conditions.
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From the 3.7 million vaccinations provided, the research team found 371 shoulder condition cases, an estimated incidence of 0.99 (95% CI, 0.89 – 1.09) per 10,000 vaccinations.
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The incidence among the adults was 1.22 (CI, 1.10 – 1.35). Among the children, the incidence dropped to 0.05 (CI, 0.02 – 0.14) — a total of four individuals in more than 750,000 pediatric vaccinations.
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Among adults, being female, older, and having more outpatient visits in the 6 months prior to vaccination, a lower Charlson Comorbidity Index, and pneumococcal conjugate vaccine were linked with increased likelihood of shoulder conditions.
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Quadrivalent influenza vaccines and elderly patients receiving multiple simultaneous vaccines in the same day were linked with greater risk for shoulder conditions.
Increased Awareness, Best Vaccine Practices, and Effective Vaccine Messaging Are Needed
The research team proposes that vaccines injected into the shoulder joint instead of the deltoid muscle may lead to immune-mediated inflammation.
“Claims of shoulder injury related to vaccine administration (SIRVA) are more than half of all claims submitted to the National Vaccine Injury Compensation Program (VICP),” Zhang noted.
“Given the high burden of shoulder conditions and the vast number of vaccinations administered, clinicians should pay attention to any factors that may further increase risk,” Zheng advised. “Unlike other vaccine side effects, shoulder pain can be prevented by safe vaccine administration.”
He urges vaccine administrators, care providers, healthcare institutions, vaccine manufacturers, and the federal government to increase their understanding of this issue, and he recommends education and training in proper vaccine administration.
“Recognizing this condition will help foster clinician and patient trust and the development of effective treatments,” he added.
Dr Anita Gupta
Anita Gupta, DO, MPP, PharmD, an adjunct assistant professor of anesthesiology and critical care medicine and pain medicine at the Johns Hopkins University School of Medicine in Baltimore, Maryland, welcomed the results. She said that during the COVID-19 pandemic, it’s important to consider that shoulder conditions after vaccination are rare.
“Public health communication about comprehensive vaccination is critically important, and we need to raise the bar: Improve on concise and clear communication on its safety and efficacy for us all,” said Gupta, who was not associated with the study. “Vaccination remains a vital public health prevention program. However, we need to better understand the short- and long-term risk factors and causal pathways, including those associated with shoulder conditions after vaccination.”
This is the first population-based study on the condition that’s based on real-world evidence, Zheng explained, and it “demonstrated the ability of artificial intelligence (NLP) to enable epidemiological research that would otherwise be impossible due to time and resource constraints.”
Zheng and colleagues acknowledge limitations of the study, which include use of administrative data, residual confounding, and the challenge of generalizing their findings to other health care settings. They recommend further research to explore risk factors and causal pathways.
Vaccine Best Practices and Injury Compensation Resources
The CDC’s Advisory Committee on Immunization Practices (ACIP) Best Practices Guidelines for Immunization and the American Society of Health-System Pharmacists (AHSP) FAQ for Optimizing COVID-19 Vaccine Preparation and Safety educate providers on best vaccination practices.
The National Vaccine Injury Compensation Program (VICP) offers financial compensation to people with serious adverse effects due to vaccines, including shoulder injury related to vaccine administration (SIRVA).
The Centers for Disease Control and Prevention funded the study. The authors and Gupta have disclosed no relevant financial relationships.
Ann Intern Med. Published online March 22, 2022. Abstract
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